canonizeFLps puts a sequence of primitive patches into
canonical form. Even if the patches are just hunk patches,
this is not necessarily the same set of results as you would get
if you applied the sequence to a specific tree and recalculated
a diff.

Note that this process does not preserve the commutation behaviour
of the patches and is therefore not appropriate for use when
working with already recorded patches (unless doing amend-record
or the like).

If commuteNoConflictsx :> y succeeds, we know that that x commutes
past y without any conflicts. This function is useful for patch types
for which commute is defined to always succeed; so we need some way to
pick out the specific cases where commutation succeeds without any conflicts.

Consider the commute square with patch names written in capital letters and
repository states written in small letters.

X
o-->--a
| |
Y' v v Y
| |
z-->--b
X'

The default definition of this function checks that we can mirror the
commutation with patch inverses (written with the negative sign)

-X X
a-->--o-->--a
| | |
Y'' v Y' v v Y
| | |
b-->--z-->--b
(-X)' X'

We check that commuting X and Y succeeds, as does commuting -X and Y'.
It also checks that Y'' == Y and that -(X') is the same as (-X)'